Please note: This information was current at the time of publication. But medical information is always changing, and some information given here may be out of date. For regularly updated information on a variety of health topics, please visit familydoctor.org, the AAFP patient education Web site.

Information from Your Family Doctor

Emergency Contraception

What is emergency contraception?

Emergency contraception is birth control used after unprotected sex to prevent pregnancy. It is taken when your regular form of birth control fails (such as a condom breaking), or when you forget to use birth control (such as not taking birth control pills). It can also be used if you were forced to have sex. Emergency contraception makes it less likely that you will get pregnant, but it does not work as well as regular birth control used correctly. It also does not protect against sexually transmitted infections (STIs).

What forms are available?

There are two main forms: pills (also called the “morning after pill”) or the copper intrauterine device (IUD). The copper IUD can be placed in the uterus by a doctor up to seven days after unprotected sex. It may be left in the uterus for up to 10 years. It is one of the most reliable forms of long-term birth control.

There are three different types of pills that can be used for emergency contraception:

Regular birth control pills can be taken at higher doses for emergency contraception. Talk with your doctor to find out if your birth control pill can be used and how many pills to take. These are taken in two doses, 12 hours apart. This should be started as soon as possible within 72 hours (three days) after unprotected sex.

Levonorgestrel is a hormone pill that is available as a single dose or two doses. The single-dose Plan B One-Step is available without a prescription for all women. The two-dose form (one brand: Next Choice) is available without a prescription (but behind the counter) only to patients 17 years or older. Those younger than 17 years need a prescription. The two doses may be taken at the same time or 12 hours apart. Levonorgestrel should be taken as soon as possible within 72 hours (three days) of unprotected sex.

Ulipristal (brand name: Ella) is available by prescription only. It is taken as a single dose. It is effective up to 120 hours (five days) after unprotected sex.

How do they work?

The pills work by slowing or stopping the release of the egg from the ovary. If the egg is not released, then it cannot be fertilized by the sperm. The IUD works by stopping the sperm from fertilizing the egg and by stopping the egg from attaching to the uterus. Emergency contraception will not end a pregnancy.

How effective are they?

The copper IUD is the most effective form. It prevents up to 99% of unplanned pregnancies. If taken correctly and on time, emergency contraceptive pills prevent about 50% to 75% of unplanned pregnancies. The pills are more effective the sooner they are taken after unprotected sex. No emergency contraceptive pill works as well as regular birth control.

What are the side effects?

Emergency contraceptive pills have side effects like regular birth control pills. They may cause nausea, cramping, headache, low back pain, and dizziness. Also, your period may come earlier or later than you expect. The copper IUD may cause cramping and irregular bleeding.

Can anyone use emergency contraception?

Anyone who takes regular birth control pills should be able to take emergency contraceptive pills. Because these pills are taken as one or two doses within 24 hours, the risks are lower than with regular birth control pills. The copper IUD should not be used if you have an STI or if you have been sexually assaulted. The IUD may increase your risk of pelvic inflammatory disease, which is a serious complication of STIs. You should not use emergency contraception if you are pregnant.

When should I see my doctor?

You should discuss emergency contraception and routine birth control with your doctor. You may want to ask about an advanced prescription for emergency contraceptive pills so that you have them if needed. If you take emergency contraceptive pills and your period is more than one week late, see your doctor to make sure you are not pregnant.